Method and apparatus for controlling the flow of volatile liquids



De z 3, 1935.

- K. E. STUART METHOD AND APPARATUS FOR CONTROLLING THE] FLOW OFVOLATILE LIQUIDS Filed Dec. 1, 193

IN VEN TOR.

Patented Deco 3, 1935 UHTED STATES METHOD AND APPARATUS FOR CONTROL-LING THE FLOW F VOLATILE LIQUIDS Kenneth E. Stuart, Niagara Falls, N.Y., assignor to Hooker Electrochemical Company, New York, N. Y., aoorporation of New York Application December 1, 1933, Serial No. 700,461

11 Claims.

In a sense, of course, all liquids are volatile, but in this applicationI shall use the term todenote any liquid that is at or near its boilingpoint.

In controlling the flow of volatile liquids, as by g at the same timeprevent the chlorine from throttling the stream, difificulty isexperienced owing to the propensity of such liquids to break into vaporphase. This is especially true when the point of control is at a higherlevel or remote from the storage container, and results from the reducedpressure upon the liquid either from increased elevation or fromfrictional loss of head or heat absorption, in the piping system. Underthese conditions, a sufficient proportion of the liquid must necessarilybreak into vaporphase to cool the remainder to its equilibriumtemperature at the reduced pressure. This may amount to very little, butin any case it will result in slugs of vapor coming along the pipe. Whensuch a slug of vapor reaches the needle valve, it for all practicalpurposes momentarily shuts ofi the flow, since the volume of the vaporis so enormous compared with that of the liquid that, notwithstandingthe higher velocity of the vapor, the weight passing the needle valve invapor phase in a given time is negligible compared with the weightpassing'in the same time in liquid phase. When it is desired, as part ofthe control, to meter the liquid, the dimculty is in creased; for themeter cannot distinguish be tween vapor and liquid and will give toohigh a reading. In some cases the meter may even be damaged by the highvelocity of the slugs of vapor.

' An instance in which such difiiculties of control frequently arise isafforded by the use of liquid chlorine under pressure in a drum, as whenused in chemical processes, such as chlorination of paper pulp. In suchprocesses accurate control of the chlorine is very important; The drumor tank car containing the chlorine is usually at ground level and thepoint of use may be several stories'higher and at a horizontal distanceof several hundred feet from the source. Not only does such a conditioninvolve a substantial reduction of pressure, but heat is liable to beabsorbed on the way. To prevent the chlorine from breaking into vaporphase at the point of controL it has hitherto been customary to raisethe pressure upon the drum or tank car well above equilibrium pressureby pumping. in air. This is objection able, as the air, even when,carefully dried, is liable to introduce moisture and the dryer itself isliable to fail. When this happens the chlorine becomes wet and attacksthe shell of the con= tainer, which not only dangerously deterioratesthe container, but contaminates the chlorine it self with iron. Evenwhen this does "not occur, the air is objectionable, as it is more orless soluble in liquid chlorine, and is given up again by the chlorineunder reduced pressure, so that it becomes necessary to provide an airtrap ahead of the point of control.

My invention therefore has for its object to obviate the necessity forexcess air pressure and breaking into vapor phase. This is accomplishedby extracting the heat of vaporization and expansion of the chlorine asit passes the needle valve, by means of a heat exchanger, from thechlorine approaching the meter. or needle valve, to cool the latterbelow its equilibrium temperature and thus reliquefy any chlorine thatmay have broken into vapor phase..

Referring to the drawing:

Figure 1 is an elevational view of a chlorine meter, needle valve andheat exchanger, arranged in accordance with my invention, the source ofthe volatile liquid being indicated diagrammatically.

Figure 2 is an elevational View of an equivalent 2o arrangement in whichthe meter is of a difierent' type.

Figure 3 is an elevational view of a needle valve and heat exchangeronly, the meter being in this case omitted.

Referring to Figure 1:

The source of chlorine is indicated at I, in this case a standard drumof the type in which it is customary to ship liquid chlorine. The heatexchanger is indicated at 2, the meter at 3, and the control valve at 4.The meter illustrated is of the type shown in my co-pending application,Serial No. 640,399.- The needle valve may be of the type shown in myco-pending application Serial No. 582,031.

In the control of flow by this method, chlorine is drawn in liquid phasefrom the drum I through pipe 5, which extends to the bottom of the drum.Pipe 5 after traversing the building and perhaps rising several stories,as indicated by the break 40 in its continuity, connects with a coil 6in the heat exchanger, which may be of copper, closely wrapped about theinner cylinder l and closely enclosed by outer cylinder 8. The exit fromcoil 6 is connected through pipe 9 to the meter. The construction of themeter is such that the flow is upward through the left leg, across thetop yoke and downward through the right leg. The meter 3 is connectedthrough pipe Hi to valve 4, thence through pipe 8 l to the annularchamber l2 be tween inner and outer cylinders l and 8 respectively. Fromthis'chamber the chlorine issues through pipe l3 and is delivered to thepoint of use, whatever it may he as the chlorination of paper pulpdescribed. in co-pending applications Serial Nos. 547,755 and 694,171.The pressure upon a chlorine drum under equilibrium conditions atordinary temperatures will be about lbs. per square inch. The drop inpressure in the.

piping may easily be 15 lbs. The back pressure to at the point of usemay be 40 lbs. leaving a net drop of 45 lbs. at the needle valve. Thiswill cause suflicient chlorine to vaporize beyond the needle valve andin the chamber I 2 to reliqueiy any chlorine that may have broken intogas on the way from drum i.

In order to illustrate that my method of control is not limited to anyone type of meter, in Figure 2 I have shown a common type of meteringorifice and U tube for indicating the flow.

To illustrate that my method of control is applicable broadly .to valvecontrol, with or without metering, in Figure 3 I have shown the valveand heat exchanger connected in accordance with my method, the meterbeing omitted altogether.

By the use of this simple arrangement of known elements, the necessityof using excess air pressure is avoided and the difllculties arisingfrom such a pressure, or without it from the chlorine breaking intobubbles, is completely obviated. The source of chlorine may be placed atany convenient point and the meter and control valve located whereverdesired within reasonable limits. The heat exchanger required is asimple, durable and inexpensive affair. Within a few seconds afterturning on a flow of chlorine that may have been standing in pipe 5 andbecome completely vaporized, the chlorine in the meter and control valvewill be 100 per cent liquid and from that time on no vapor can occur atthis point. The control of the flow of chlorine is thereby renderedsimple, accurate and reliable.

What I claim is: l. The method of metering the flow of volatile turebelow the equilibrium temperature of saidfluid at the up-stream side ofsaid point by efleoting a transfer of heat from said stream to vaporizeliquid of the stream leaving said point.

3. The method of metering the flow oi fluid, including componentsthereof in liquid and vapor phase, which includes the step of coolingthe stream of fluid approaching the point of metering to a temperaturebelow the equilibrium temperature of said fluid corresponding to thepressure at the up-stream side of said point by eifecting a transfer ofheat from said stream-*to vaporize liquid of the stream leaving saidpoint.

4. The method of metering the.flow of fluid.

including components thereof in liquid and vapor phase, which includesthe step of cooling the stream of fluid approaching the point ofmetering to a temperature-below the equilibrium temperature or saidfluid corresponding to the lowest pressure likely to develop at theup-stream side of said point, thereby reliquefying the fluid in vaporphase and stabilizing the stream in liquid phase, by effecting atransfer c1 heat from said stream to vaporize liquid of the streamleaving said point.

5. The method of metering the flow of volatile fluids which includes thestep of vaporizing a part of the stream of fluid leaving the point ofmetering and eflecting a transfer of heat to said stream from thestreamof fluid approaching said point to cool said last mentioned stream to atemperature below the equilibrium temperature of said fluid at theup-stream side of said point.

6. The method of metering the flow of volatile fluids which includes thestep of restricting the flow for regulation thereof, thereby causingdrop of pressure and vaporization of a part of the stream of fluidleaving the point of restriction, and efiecting a transfer of heat tosaid stream fromthe stream offluid approaching said point of restrictionto cool said last mentioned stream to a temperature below theequilibrium temperature of said fluid at the up-stream side of saidpoint of. restriction and metering the stream approaching said point ofrestriction in liquid phase.

7. The method of controlling the flow of a stream of volatile fluidwhich comprises regulating the rate of flow thereof, eifecting a heattransfer from the stream approaching the point of regulation to thestream leaving said point of regulation and metering'said approachingstream in liquid phasebetween the point of heat transfer and said pointof regulation.

8. The method of metering a stream of volatile fluid includingcomponents thereof in liquid and vapor phase which comprises reducingthe pressure upon said stream and vaporizing a portion thereof,effecting a heat transfer from said stream in advance of the point ofpressure reduction to supply the heat of vaporization of said vaporizedao portion, and metering said stream between said point of heat transferand said point of pressure reduction in liquid phase.

9. The method of metering and controlling, inv

liquid phase, at a point higher than its point of origin, the rate offlow of, a stream of volatile fluid under equilibrium conditions oftemperature and pressure, which comprises regulating said flow,efiecting a heat transfer from the stream approaching the point ofregulation to the stream 40 leaving said point of regulation andmetering said approaching stream in liquid phase between the point ofheat transfer and said point of regulation.

10. The method of metering and controlling in liquid phase, at a pointremote from its source, the rate of flow of a stream of volatile fluidsfrom a source under equilibrium conditions of temperature and pressure,which consists in regulating said flow, effecting a heat transfer fromthe stream approaching the point of regulation to the stream leavingsaid point oi regulation and metering said approaching stream in liquidphase between the point of heat transfer and said point of regulation.

11.' An apparatus for metering and controlling the rate of flow of astream of volatile liquid comprising a heat exchanger, a conduit forconveying said stream theret ugh, a meter, 9. conduit for conveying saidream from said heat exchanger to said meter, a control valve, a conduitfor conveying said stream from said meter to said control valve, aconduit for conveying said stream from said control valve through saidheat exchanger and a conduit for delivering said 66 stream from saidheat exchanger, whereby the pressure upon said stream is reduced bysaid. control valve and a portion of said stream vaporized at and beyondsaid control valve and the heat-of vaporization of said portion is ex-70 tracted from the stream approaching said meter to maintain said lastmentioned stream in liquid phas KENNEI'H n. STUART.

